Dialysis is a treatment that removes waste products, toxins such as urea, creatinine, and uric acid, and excess fluid that accumulate in the body's blood and tissues as a result of kidney failure or kidney dysfunction. Dialysis treatment is critical for a person, who has kidney failure or reduced kidney function, because a person cannot continue to live without the filtration functions provided by the kidneys.
Hemodialysis is one type of dialysis treatment where toxins are filtered from a patient's blood extracorporeally using a hemodialysis machine. The hemodialysis machine generally contains a computer, fluid pumps, blood lines, dialysate lines, a dialyzer, and drain lines for discarding the large volumes of dialysis solution used in each treatment. The patient's circulatory system is connected to a hemodialysis machine via catheters or fistula needles and the patient's blood is pumped continuously through the hemodialysis machine. The blood passes through a dialyzer containing semi-permeable membranes in the hemodialysis machine. The semi-permeable membranes separate the blood on one side from dialysis solution on the other side. The dialyzer removes the waste, toxins and excess water from the blood, and then returns the blood to be re-infused in the patient. The waste products and toxins transfer out of the blood through the semi-permeable membrane into the dialysis solution, which is then discarded. A large amount of dialysate, i.e., approximately 90-120 liters, is used by most hemodialysis machines during a single dialysis treatment. The used or spent dialysate is then discarded. Hemodialysis treatments typically are conducted three or four times a week at service centers under the supervision of clinicians. Each treatment takes approximately four to six hours and requires a large supply of dialysis solution or a continuous source of water. The spent dialysate is typically discarded.
Peritoneal dialysis is another type of dialysis treatment where toxins and excess water are filtered from a patient's blood and organs by introducing dialysis solution containing glucose or dextrose and other electrolytes into the peritoneal cavity allowing the dialysis solution to dwell for a period of time. The abdominal cavity has an exceptional blood supply where urea and other toxins in the blood transfer to the dialysis solution. Patients either use pre-prepared dialysis solution or prepare the dialysis solution using purified water from their home. Peritoneal dialysis treatments typically are conducted at the patient's home on a daily basis and require 10-15 liters of dialysate per treatment. The spent dialysate is typically discarded.
Continuous Ambulatory Peritoneal Dialysis (CAPD) and Continuous Cycling Peritoneal Dialysis (CCPD) are two types of peritoneal dialysis that allow the dialysis solution to dwell in the peritoneum for a period of time. During CAPD and CCPD, dialysis solution is introduced into the peritoneum and, after a period of time, the dialysis solution is drained and discarded. Then, new dialysis solution is introduced into the peritoneum. During each treatment, the fill, drain and dwell sequence is repeated as prescribed. In CAPD, the filling, dwelling and draining are done manually. In CCPD, the filling, dwelling and draining is done by a machine.
Another type of peritoneal dialysis is Continuous Flow Peritoneal Dialysis (CFPD). During CFPD, dialysis solution is introduced into the peritoneum using two separate catheters or a double lumen catheter through the inflow catheter while the outflow catheter is clamped. Once the desired fill volume is achieved, the outflow catheter is opened, and the inflow and outflow flow rates are maintained relatively constant so that the dialysis solution is continuously pumped through the peritoneum. CFPD is typically performed at high flow rates and requires very large volumes of dialysis solution.
The use of certain devices to regenerate spent dialysis solution from hemodialysis and/or peritoneal dialysis is known in the art. For example, the Redy™ (REcirculating DYalysis) Sorbent System (Blumenkrantz et al., Artif Organs 3(3):230-236, 1978) includes a sorbent cartridge with multiple layers for removing toxins and other waste products from dialysis solution. Sorbent cartridges require a significant amount of material and layers. Almost half of the material in the cartridge is zirconium phosphate, which binds and removes ammonia.
A need exists to provide improved dialysis systems. This can be accomplished by reducing the amount of water or dialysis solution needed for each treatment and by reducing the amount of sorbent material needed for each treatment. Each dialysis treatment requires a large supply of dialysis solution or a continuous source of water. A patient undergoing hemodialysis three times a week requires approximately 270-360 liters of dialysate a week. A patient undergoing peritoneal dialysis requires approximately 70-105 liters per week.